Quite interesting the the majority of people have picked sedimentary as the most common. My vote is igneous based on the ocean crust and granite batholiths which underlie mountain chains.
That aside, it had me wondering about where the definition of a 'rock' ends. At the Moho? What about serpentinite and ophiolite suites. At the core/mantle boundary? That gets my vote as the outer core is liquid and therefore not (in my book) a rock. But what about the inner core? solid again but dominantly metal, does this classify as a rock?
 As it's exam season I'll finish by saying...discuss!
It is an interesting survey indeed! I was torn between igneous and metamorphic as I considered the mantle as rock. I stopped coutning rock at the c/m boundary. What is the mantle: igneous or metamorphic?
Come on Guys and Gals. Sedimentary!!! A simple piece of deduction should help you relise that this is not the case. Most sedimentary rocks are formed through weathering of other rock types (though not exclusively). With this in mind there has to be a vast amount of other rock types to provide the material for sedimentary rocks, they then only form a thin veneer on top of those other rock types. Also taking into account the loss of some of the minerals to dissolving and being held in concentration it can not possibly be sedimentary. Just because in a lot of cases the ground immediately below us seems to be sedimentary if you go down deeper the crust consitsts largely of igneous rocks. All oceanic crust is igneous (yes serpentinite is an obvious exception) and a vast amount of the continents are igneous. In fact I believe that igneous rocks make up 95% of the Earth's crust. As for the mantle, the rock that we end up with on the surface is certainly igneous (peridotite) whether or not it is like this at depth and under pressure is a different question all together.
Your teacher is wrong. The mantle is solid. It is not molten. We know this because it transmits shear waves.
A rheid is defined as a solid that deforms by viscous flow. The mantle material behaves plastically. Long term it appears to flow like a liquid but this does not make it one.
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The latest poll
Wed, 05/02/2007 - 13:51Quite interesting the the majority of people have picked sedimentary as the most common. My vote is igneous based on the ocean crust and granite batholiths which underlie mountain chains.
That aside, it had me wondering about where the definition of a 'rock' ends. At the Moho? What about serpentinite and ophiolite suites. At the core/mantle boundary? That gets my vote as the outer core is liquid and therefore not (in my book) a rock. But what about the inner core? solid again but dominantly metal, does this classify as a rock?
 As it's exam season I'll finish by saying...discuss!
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It is an interesting survey
Wed, 05/02/2007 - 13:59It is an interesting survey indeed! I was torn between igneous and metamorphic as I considered the mantle as rock. I stopped coutning rock at the c/m boundary. What is the mantle: igneous or metamorphic?
Geologists are gneiss!!
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Cum hoc ergo propter
Wed, 05/02/2007 - 14:44Cum hoc ergo propter hoc
Come on Guys and Gals. Sedimentary!!! A simple piece of deduction should help you relise that this is not the case. Most sedimentary rocks are formed through weathering of other rock types (though not exclusively). With this in mind there has to be a vast amount of other rock types to provide the material for sedimentary rocks, they then only form a thin veneer on top of those other rock types. Also taking into account the loss of some of the minerals to dissolving and being held in concentration it can not possibly be sedimentary. Just because in a lot of cases the ground immediately below us seems to be sedimentary if you go down deeper the crust consitsts largely of igneous rocks. All oceanic crust is igneous (yes serpentinite is an obvious exception) and a vast amount of the continents are igneous. In fact I believe that igneous rocks make up 95% of the Earth's crust. As for the mantle, the rock that we end up with on the surface is certainly igneous (peridotite) whether or not it is like this at depth and under pressure is a different question all together.
Cum hoc ergo propter hoc
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Perovskite
Wed, 05/02/2007 - 17:27By volume it is perovskite - all the way from 660km (Spinel-Pervoskite Transition) to 2900km (Core-Mantle Boundary)
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for volume, should be Igneous, but for commonness, should be
Mon, 07/02/2007 - 09:45Sedimentary
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The Mantle
Mon, 11/05/2007 - 15:00Is the mantle not Rheid? Short term solid, long term liquid. It's about 98% molten I believe, but not entirely sure of my facts.
 I've been informed it has the consistency of Ice Cream by my teacher!
 I think this must be igneous, Sedimentary rocks take too long to form, and, the oceanic plates are largely igneous i believe? Is this correct?
 First Post, Pete
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The mantle is solid
Mon, 11/05/2007 - 15:57Pete,
Your teacher is wrong. The mantle is solid. It is not molten. We know this because it transmits shear waves.
A rheid is defined as a solid that deforms by viscous flow. The mantle material behaves plastically. Long term it appears to flow like a liquid but this does not make it one.
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Sorry
Fri, 11/09/2007 - 11:58Just read what i typed. It's defined as 98% SOLID. And yes S waves prove that this must be so, due to elastic incompressabilty and rigidity.
 pretty sure about the rheid idea though, is this something you've come across before?
 thanks for pointing this out
pete
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Rheid
Sat, 11/10/2007 - 10:49I wasn't disputing that the mantle is a rheid. I was just pointing out that a rheid is a solid and you were suggesting that the mantle was a liquid
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i think its sedementaty
Thu, 07/09/2009 - 21:24i think its sedementaty because all the rocks would be pressed together afer time wheather they were metamorphic or ignous